For which one of the following compounds standard enthalpy change (∆H∘) can be measured directly by calorimeter?

Explanation

Option D, MgO (magnesium oxide), is correct because its standard enthalpy change (∆H∘) can be measured directly by a calorimeter.Calorimetry is a technique used to measure the heat absorbed or released during a chemical or physical process. In the case of MgO, it is formed from its elements, magnesium (Mg) and oxygen (O2), through a chemical reaction:2Mg(s) + O2(g) ⟶ 2MgO(s)The heat released during this reaction can be measured directly using a calorimeter. The calorimeter allows for the precise measurement of the temperature change that occurs during the reaction, which is directly related to the enthalpy change (∆H∘) of the reaction.Options A, B, and C are incorrect because the standard enthalpy change of formation (∆H∘f) for these compounds involves reactions that are not as straightforward or easily measurable using a calorimeter.